Apolipoprotein E (apoE) is produced abundantly in the liver and brain. It plays important roles in the metabolism and redistribution of lipids. In the brain, apoE has been implicated in development, regeneration, and neuroprotection. Recently, we have identified a novel function of apoE, i.e. centrally administered apoE potently suppresses food intake and body weight without eliciting signs of toxicity, and blocking the action of endogenous brain apoE with its specific antibody increases food intake. Mice with a targeted deletion of the apoE gene consume more food and weigh more than wild-type mice. These results imply that apoE plays an essential role in the control of food intake and body weight. Thus, we speculate that insufficient apoE production may render an animal vulnerable to the development of obesity. Our long-term goal is to identify pharmacological targets for suppressing appetite as a means of preventing and treating obesity. The objective of this specific application is to identify the mechanism(s) mediating apoE's effect in the control of food intake and body weight. The first specific aim will assess the hypothesis that increased food consumption in obese animals is due in part to reduced apoE signaling in the hypothalamus, a central area regulating energy homeostasis. The second specific aim will evaluate the hypothesis that hypothalamic apoE exerts its anorectic function by influencing catabolic regulatory neuropeptides and/or their receptors. The third specific aim will identify the mechanisms that mediate apoE's anorectic action by determining apoE-relevant receptor(s) and signal transduction pathways. The proposed work is innovative because it assesses a novel physiological function of apoE in the brain. In addition, it takes advantage of the rich research environment in the University of Cincinnati Obesity and Lipid Research Centers and employs available experimental methods and several unique animal models. Moreover, outcomes of this research will have a positive impact on the field of obesity research because the fundamental new knowledge is expected to facilitate the development of preventive and therapeutic interventions to address the epidemic of obesity and, consequently, to decrease health care costs in the United States.